Decorative effects in polystyrene moldings



Patented Aug. 28, 1945 MoLnmGs Russen n. Bradshaw, Midland, Mich., assigner to 4 The Dow lChemical Company, Midland, Mich., acorporation of Michigan ,Y .Y

No Drawing. vOriginal application February 24, 1939, Serial N0. 258,212. Divided and this 8.1)-

`plication December 30, 1942, Serial No. 470,645

9 claims.' (ci. 26o-41) v This invention relates to the production `of decorative effects in polystyrene moldings.

An object of the invention is to provide a sim-l ple inexpensive method of preparing DOlyStyrene molded objects having a lustrous pearlescent appearance.

According to the invention, polymerized styrene is mixed together with a small proportion of a. hymolal salt and the resulting mixture is molded under heat and pressure into objects having a -high surface luster and a. pleasing nacreous ap.-

pearance resembling mether-of-pearl.

In practice, a charge of polystyrene and a small proportion, e. g., between about 0.5 and about' l0 per cent by weight oi' a hymolal salt is heated to a temperature at which the polystyrene isgof a plastic or doughlike consistency, and is then subjected to mechanical working soas to incorporate the hymolal salt into the plastic mass. This working is preferably carried out in a kneading machine or on heated rolls, but other types of mixingl apparatus may be employed. After the mixing operation, the plastic mass maypbe molded directly into objects of any desired size or shape, either by compressionor injection-molding, according to known, procedures. Alternatively, after mixing, the plastic mass may be cooled and ground or otherwise reduced to a powder, which is then used in subsequent molding operations.

A variety of decorative effects may be produced in polystyrene according to the invention by varying the proportion of hymolal salt used and by carefully controlling the mixing and molding procedures. For example, when the polystyrene and hymolal salt are kneaded together for a short time only so that mixing is incomplete, i. e. so that the resulting product is non-homogeneous and the mixture is then molded, objects of delicate striated or marbleized irldescent appearance are obtained. However, when a thorough mixing is carried out so as to produce ahomogeneous plastic mass, the articles molded therefrom resemble natural pearl. Further interesting effects may be produced by incorporating dyes, pigments, plasticizers, etc., in the charge of polystyrene and hymolal salts prior to or during the mixing procedure.

^ the trade-names oi Drei t, Duponol M. E., and

the like.\l;n practice, the hymolal salt is preferably added y'to the polystyrene in the form of whips',

flakes, beadsf or powder,` although other forms may be used.

Polystyrene molded objects according to the invention, in additiontovhaving the .pleasing appearance described, are stable towards light and are unaffected by water or aqueous solutions. They possess the further, advantage that they are easier to eject from the \mold in which they are formed than ordinary polystyrene moldings.

Other modes ofapplying Ithe principle of the invention may be employed instead of those explained, change being made as regards the details disclosed, provided the method or product stated in any of the following claims, or the equivalent thereof be employed.

'I'his application is a division of my co-pending application Serial No. 258,212, iiled February 24,

1939, now Patent No. 2,330,108 issued September v 1. A molded obicct'characterized by a nacreous sheen and essentially consisting of polystyrene having vincorporated, therein between about 0.5 and about 10 per cent by weight of a salt selected from the groupconslsting of the sodium, potasslum, and magnesium salts of sulfated alkyl alcohols containing at least 12 carbon atoms in the alkyl radical thereof, this salt being present in an amount effective to cause a nacreous sheen.

2. A molded object characterized by a nacreous sheen and essentially consisting of parts of polystyrene and 0.5 to 10 parts ofa sodium salt oia sulfated alkyl alcohol containing at least 12 carbon atoms in the alkyl radical thereof, this salt being present in an amount eilective to cause a nacreous sheen.v 3. A product according to claim 2 wherein the salt is sodium cetyl sulfate.

4. A molding powder suitable ior'molding into objects having a nacreous appearance and essen.- tially consisting of polystyrene having incorporated therein between about 0.5 and about 10 iridescent appearance and consisting essentially of polystyrene having non-homogeneously mixed therewith between about 0.5 and 'about 10 per cent by weight of a salt selected fromthe class consisting of the sodium, potassium, and magnesium salts of s ulfated alkyl alcohols containing Y' V` at least l2 carbon atoms in the alkyl radical thereof.

6. A process of preparing a polystyrene plastic characterized by a. nacreousj sheen which comprises forming a plastic mixture-consisting essentiallyof polystyrene and from about 0.5to about assenso l0 percent. by weightthereofof a salt selected from the class consisting ofthe sodium, potassiurn, and magnesium salts` of sulphated: alkyl alcohols containing at least ll2 carbon atoms in the alkyl radical thereof, Athis salt'beingpresentg in an amount effective to cause a nacreous sheen;`

and thereafter molding said plastic mixture.

" carbon atoms in the alkyl radical thereof 1to in-` 7. A method of forming .apolystyrene'molding powder for producing objects characterized by a nacreous sheen which comprises heating polykflietween about 0.5v and about 10 per cent by weight of a salt selected from the group consisting of the sodium, potassium. and magnesium salts of sulphated alkyl alcohols containing at least l2 corporate the said salt into the plastic mass, the

`said kneading being carried out for a time insufcentto 'produce a homogeneous mixture. and

'the 'salt being present in an amount eilective to cause a nacreous sheen, and molding the mixstyrene to a temperature at which it is plastic. and kneading the same together with between about 0.5 and about 10 per `centloy weight of a salt selected from the group consisting of the sodium, potassium,y and magnesiumsalts of sulphated alkyl alcohols containing at least 12 car- -f bon atomsin the alkyl radical thereof. this salt,

1 beingpresent in an amount eiective to cause y j ture thus` obtained into objects by application A of heat and pressure.

-9` A molded object characterized by a nacreous sheen and essentially consisting of 100 parts of polystyrene and from 6.5 to 10 par-ts of sodium lauryl sulphate, vthe latter being present in an amount eiective to cause a nacreous sheen.

t RUSSELL R. BRADSHAW. 

